Oil and gas exploration has increased considerably in the past several years due to the energy shortage and dependency upon foreign oil. Large oil and gas wells are being drilled in the oceans and other large bodies of water a considerable distance offshore by use of floating oil rigs. These offshore oil and gas rigs, especially those drilling for oil, present serious environmental problems. Leaks can occur in the oil well pipe which extends between the derrick and bore hole in the ocean or lake bottom. Such leaks could result in a considerable amount of oil being discharged into the ocean or lake affecting the marine and plant life thereof and also the surrounding shoreline and beaches before the leak could be effectively stopped.
Shut-off valves could be placed in various sections of this pipe string extending between the ocean or lake bottom and derrick if desired to provide a safety shut-off for the flow of oil. However, such valves provide an inherent trouble spot due to the various connections required to mount them in between pipe sections. Also these valves could become corroded with the passage of time and become inoperable when an emergency arises. Furthermore, such valves if placed at spaced locations along the well pipe, would increase the cost of the well in addition to presenting a possible "weak link" in the pipe string.
Therefore, it is desirable that some type of shut-off valve be provided for the well pipe which will not interfere with the normal construction, drilling and operation of the well, and which can be used to plug the pipe at any location along the pipe length, and which need not be a permanent part of the pipe.